In FY 2019, we continued our investigation of virulence factors that contribute to Staphylococcus aureus pathogenesis and immune evasion. The focus is on understanding which factors define the virulence potential of highly virulent MSSA and MRSA clones, in particular of community-associated MRSA. Much of our work is currently still focussed on phenol-soluble modulins (PSMs), toxins that we discovered in 2007. We collaborate with a series of researchers in different fields, analyzing the contribution of PSMs to different phenotypes. Current efforts in our own lab are aimed at understanding the mechanism of the PSM exporter and the involvement of PSMs and quorum-sensing in staphylococcal sepsis. New directions of research in the past FY included investigation of interactions of staphylococci with other bacteria, for example with bacilli during intestinal colonization.